1. Field of the Invention
The present invention relates to color-stabilized compositions which comprise a halopropynyl compound, such as 3-iodo-2-propynyl butylcarbamate (hereinafter referred to as “IPBC”), and to methods for making and using the compositions.
2. Description of the Related Art
Iodopropynyl carbamates are widely employed as preservatives in coating compositions. In particular, 3-iodo-2-propynyl butylcarbamate (hereinafter referred to as “IPBC”) has achieved worldwide commercial success. IPBC was first disclosed and claimed in U.S. Pat. No. 3,923,870, issued to William Singer on Dec. 2, 1975 and assigned to the assignee of the present patent application.
While IPBC offers many advantages over other biocides, it is prone to a visually-detectable discoloration that is reportedly initiated or accelerated by exposure to sunlight or other ultraviolet light sources. Although light-related discoloration of IPBC-containing products is only sporadically encountered, and sometimes disappears after a period of weeks, it is of major concern to coating manufacturers. Because elemental iodine is yellow to brown, and because the tri-iodide anion (I3−) is a deep yellowish-brown color, some previous researchers have speculated that light-related discoloration of IPBC is accompanied by the formation of elemental iodine or other free radical fragments.
U.S. Pat. No. 4,276,211, issued to William Singer et al. on Jun. 30, 1981 and assigned to the assignee of the present application, describes the use of epoxides as color stabilizers for iodoalkynyl carbamate fungicides in paint compositions and coatings. U.S. Pat. No. 4,276,211 patent is hereby incorporated by reference in its entirety, and specifically for its teachings regarding stabilizers for IPBC.
U.S. Pat. No. 4,297,258, issued to Long, Jr., describes the use of epoxy-based acid scavengers to reduce IPBC yellowing or discoloration.
As another example, U.S. Pat. No. 5,554,784, issued to Gruening, describes a method for preparing IPBC that reportedly minimizes discoloration or yellowing in coating compositions exposed to sunlight.
Some previous researchers have suggested adding an ultraviolet absorber or a light stabilizer to IPBC to prevent or retard discoloration. For example, U.S. Pat. No. 6,472,424 B1, issued to Gaglani et al. and assigned to the assignee of the present application, describes benzylidene camphor as an IPBC stabilizer. Also, see U.S. Pat. No. 6,353,021 and U.S. Pat. No. 5,938,825, both issued to Gaglani et al., and assigned to the assignee of the present application, for recommendations regarding other IPBC stabilizers. U.S. Pat. Nos. 6,472,424 B1; 6,353,0212; and 5,938,825 are hereby incorporated by reference in their entirety, and specifically for their teachings regarding stabilizers for IPBC.
Other researchers favor absorbing, impregnating, or encapsulating IPBC within or on various solid carrier materials. For example, published WIPO patent application WO 2010/147820 A1 describes a stabilized biocidal dispersion comprising a biocide coated or adsorbed onto stable sub-micron carrier particles selected from metal oxides such as zinc oxide, titanium dioxide, cerium dioxide, and the like. As another example, U.S. Pat. No. 7,429,392 B2, issued to Baum et al., describes a coating material characterized in that it contains a biocide which bonds to solid particles in a carrier material and is released in a delayed manner. U.S. Pat. No. 7,429,392 B2 patent is hereby incorporated by reference in its entirety, and specifically for its teachings regarding biocides which are released from solid particles in a delayed manner.
Published patent application WO 2010/133548 A2 describes a production method for the preparation of small polymer microcapsules with an oil core and solid microspheres, comprising high amounts of biocide by internal phase separation from emulsion droplets with ethyl acetate as a solvent. Reportedly, the size of the microcapsules and microspheres can be controlled with a high degree of accuracy between 0.2-20 microns in diameter and the microparticles are well suited for protecting coatings.
Published patent application WO/2010/148158 A1 describes a process for the preparation of a sustained-release biocidal composition containing microencapsulated biocide, which comprises the steps of: (i) adsorbing the biocide onto an inert carrier and grinding to attain a desired particle size with a ratio of biocide to inert carrier in the range of about 1:99 to about 99:1; (ii) optionally coating the biocide and inert carrier with an appropriate amine or imine compound or a water resistant film forming polymer, and dispersing the encapsulated biocide in an aqueous medium in the presence of a dispersing agent; (iii) adding at least one thickening agent to re-disperse the encapsulated biocide; and (iv) preparing an aqueous or solvent based sustained release biocide dispersion.
Despite the impressive achievements of previous researchers over a period spanning thirty years, a need still exits for an IPBC composition that resists discoloration in end-use coatings formulations.